The crystal structure of a novel dimeric β-D-galactosidase from Paracoccus sp. 32d (ParβDG) was solved in space group P212121 at a resolution of 2.4 Å by molecular replacement with multiple models using the BALBES software. This enzyme belongs to glycoside hydrolase family 2 (GH2), similar to the tetrameric and hexameric β-D-galactosidases from Escherichia coli and Arthrobacter sp. C2-2, respectively. It is the second known structure of a cold-active GH2 β-galactosidase, and the first in the form of a functional dimer, which is also present in the asymmetric unit. Cold-adapted β-D-galactosidases have been the focus of extensive research owing to their utility in a variety of industrial technologies. One of their most appealing applications is in the hydrolysis of lactose, which not only results in the production of lactose-free dairy, but also eliminates the `sandy effect' and increases the sweetness of the product, thus enhancing its quality. The determined crystal structure represents the five-domain architecture of the enzyme, with its active site located in close vicinity to the dimer interface. To identify the amino-acid residues involved in the catalytic reaction and to obtain a better understanding of the mechanism of action of this atypical β-D-galactosidase, the crystal structure in complex with galactose (ParβDG-Gal) was also determined. The catalytic site of the enzyme is created by amino-acid residues from the central domain 3 and from domain 4 of an adjacent monomer. The crystal structure of this dimeric β-D-galactosidase reveals significant differences in comparison to other β-galactosidases. The largest difference is in the fifth domain, named Bgal_windup domain 5 in ParβDG, which contributes to stabilization of the functional dimer. The location of this domain 5, which is unique in size and structure, may be one of the factors responsible for the creation of a functional dimer and cold-adaptation of this enzyme.
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http://dx.doi.org/10.1107/S2059798316012535 | DOI Listing |
Inorg Chem
January 2025
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
Incommensurately modulated crystals are a rare class of materials that are notoriously difficult to characterize properly. We have synthesized two new incommensurately modulated compounds, RbTaSe and CsTaSe, based on the MQ (M = Nb, Ta; Q = S, Se) unit using high-temperature solid-state synthesis. Using superspace crystallography in combination with second harmonic generation measurements, we confirmed both materials to be noncentrosymmetric, falling into the superspace group 1(αβγ)0, while the basic cell suggests 2/.
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January 2025
Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, United States; Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States. Electronic address:
The mitochondrial flavoenzymes proline dehydrogenase (PRODH) and hydroxyproline dehydrogenase (PRODH2) catalyze the first steps of proline and hydroxyproline catabolism, respectively. The enzymes are targets for chemical probe development because of their roles in cancer cell metabolism (PRODH) and primary hyperoxaluria (PRODH2). Mechanism-based inactivators of PRODH target the FAD by covalently modifying the N5 atom, with N-propargylglycine (NPPG) being the current best-in-class of this type of probe.
View Article and Find Full Text PDFSci Rep
January 2025
IBM T. J. Watson Research Center, Yorktown Heights, NY, 10598, USA.
The development of high-brightness electron sources is critical to state-of-the-art electron accelerator applications like X-ray free electron laser (XFEL) and ultra-fast electron microscopy. Cesium telluride is chosen as the electron source material for multiple cutting-edge XFEL facilities worldwide. This manuscript presents the first demonstration of the growth of highly crystalized and epitaxial cesium telluride thin films on 4H-SiC and graphene/4H-SiC substrates with ultrasmooth film surfaces.
View Article and Find Full Text PDFNat Commun
January 2025
Laboratory for Chemistry and Life Science, Institute of Integrated Research, Institute of Science Tokyo, Yokohama, 226-8501, Japan.
Atomically flat two-dimensional networks of boron are attracting attention as post-graphene materials. An introduction of cations between the boron atomic layers can exhibit unique electronic functions that are not achieved by neutral graphene or its derivatives. In the present study, we propose a synthesis strategy for ion-laminated boron layered materials in a solution phase, which enables the preparation of analogs by changing the alkali-metal species.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
January 2025
Xiamen University, Department of Chemistry, Siminnan Road 422, 361005, Xiamen, CHINA.
Quintulene is a quintuply symmetrical cycloarene with a positively curved molecular geometry. First described by Staab and Sauer in 1984, its successful synthesis was not achieved until 2020. Due to the challenges posed by its positive curvature, structural extensions of quintulene have been studied rarely.
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